Implementation

simple_midi_read is a single header library in the style of stb. To add to your code, put simple_midi_read.h somewhere in your codebase, and include it anywhere you need to use it. In exactly one of the files that you include it in, add

#define SMR_IMPLEMENTATION

before the include. So your code in that file should look like:

#include ...
#include ...
#define SMR_IMPLEMENTATION
#include "simple_midi_read.h"

The header file will then build along with the rest of your code.

Usage

To read a MIDI file:

struct smr_midi_data midi_data;
int result;
result = smr_read_file("path/to/midi_file.mid", &midi_data);
if (result != 0)
{
    print("Error!");
}

Important! The library does not manage the memory of smr_midi_data, so to free that memory, you must call:

smr_free_midi_data(&midi_data);

An smr_midi_data struct is laid out much like a MIDI file itself, minus the byte packing and variable length types (except strings). Here's a good resource to familiarize yourself with the MIDI file spec. (Take note especially of the Delta times section, which explains how time works in a MIDI file.)

The smr_midi_data struct contains an array of tracks (smr_midi_data.tracks, of length smr_midi_data.ntracks), and each track contains an array of events (smr_track_data.events, of length smr_track_data.nevents). Every event in the array is an smr_event, but you can get the type of event using the enum smr_event.event_type. From there, smr_event uses unions to give you access to any relevant variable to that type of event. For instance, if the event is type SMRE_midi_note_on, you can get the event's smr_event.note and smr_event.velocity; if the event is type SMRE_midi_controller, you can get the event's smr_event.controller and smr_event.value. More commenting of these events in the code is needed, but for now you can refer to the MIDI file spec, as well as test.c, to get an understanding of how these different events work.

Miscellaneous

• This library requires C11 or later to compile, to take advantage of anonymous structs and unions (which is critical to how I've structured smr_event and smr_midi_data). Without that, you would also need C99 for the fixed-size types (uint32_t, etc.). If you require an older version of C, and/or have ideas on how to better structure those aspects of the code, I'm open to hearing it.
• There are currently two allocations that happen when loading a file - one to load the raw file data into memory, and one to create the block of memory for storing the smr_midi_data track array, event array, and strings (smr_midi_data._mem_block). It's on my to-do list to offer the user a way to define their own malloc replacement.
• If you would rather read from a memory block instead of a file, you can call smr_read_byte_array directly. This will skip the allocation in smr_read_file and bring your total number of allocations to 1.